With “40-Year-Old Virgin” and “Knocked Up,” writer/director Judd Apatow created a special comedic identity that combined slacker geek sentimentality with crude, winding improvisational stings. It suited him well at the box office, but “Funny People” bravely detaches from Apatow’s comfort zone, though in a crafty manner that perhaps doesn’t provide an intensive genre-shifting challenge for the filmmaker. However, there’s just enough of a shove into uncharted waters of callous behavior to maintain an intriguing bite to the essential rolls of laughter.

George Simmons (Adam Sandler) is a stand-up comic who’s made it to the big time, becoming a worldwide celebrity through a battery of box office smashes and stage dominance. Diagnosed with a rare blood disease, George is left to contemplate his lonely existence, looking back on ex-girlfriend Laura (Leslie Mann) as a major point of unfinished business in his life. Stumbling upon Ira (Seth Rogen, doing a delightful take on starry-eyed surprise), a struggling stand-up, George finds a makeshift comedic soul mate, taking the inexperienced funny man into his life for jokes and companionship. Still holding onto medical hope, George decides to seek out Laura and sever her seemingly unhappy marriage to Aussie bully Clarke (Eric Bana), while Ira stands in firm protest, but unable to challenge his boss and unwilling to torpedo his amazing show business education.

There’s a filmmaking maturation going on for Apatow during “Funny People” that showcases the director looking toward the work of James L. Brooks for inspiration, a man who always treads the fine line between comedy and heartache. In pursuit of his lofty tonal goals, Apatow retreats to his past life as a stand-up comic for support, setting “Funny People” in this world of egos, competition, and anxiety. The insight is outstanding; the picture excels at a lived-in mood of tentative steps between jealous colleagues vying for the spotlight. Instead of a parade of cuddly man-child characters, the feature is populated with the likes of George: a burnt, spent man who wields his power of fame knowingly and selfishly.

Apatow is intrigued with George’s anesthetized humanity, and how the man who has everything at his fingertips approaches the finality of death. It’s a stunning performance from Sandler (no doubt drawing from his own experience), who imparts George with captivating flavors of bitterness, shame, and work-the-room charm that create a vividly three-dimensional character, avoiding easy answers and certainly swatting down a proper Hollywood arc of redemption. Perhaps this is where “Funny People” might confuse those expecting traditional (and superb) Apatow comfort food. George is a bastard. While he reaches a summit of personal potential, he remains this hardened creature of self-centeredness, emerging from a knowing screenplay that grasps the soul of a comedian and the gig’s destructive tendencies. It’s a tremendously complex characterization that extends to the supporting cast, who are there to assist with the hoots, but take a few potent moments of discord for themselves.

“Funny People” isn’t precious and its luxurious 145 minute running time just flies by. Thankfully, there’s a bundle of laughs to help ease into the hazy psychological discomfort, with the entire cast getting in their fair share of punch lines, including amusing supporting work from Jason Schwartzman, Jonah Hill, and Aubrey Plaza. It’s wonderful to watch the cast interact so fluidly, yet committed to an awkward sense of detachment that plagues the vocation. “Funny People” nails some priceless clumsy moments through improvs and situational uneasiness, but it’s never a sitcom. Apatow finds reality as much as possible, though he indulges his mischievous sense of humor here and there, always to uproarious results.

The film is divided into three distinct acts, giving Apatow some air to suitably build a tangled web of urgency for George and Ira. The first act introduces the relationship between the comics and feels out the death sentence for George; the screenplay hitting bittersweet notes of remorse and frustration for the character. Act two brings George back to Laura’s arms, where the comic perceives personal salvation through forgiveness, rekindling a romance that never received its proper closure. It’s a lengthy detour, but one that further accentuates George’s self-serving attitude and muddled vision of accomplishment. The last act has Apatow searching for an opening to tie dangling plot threads together, but it’s rushed and condensed, taking the knots out of the storyline too swiftly, grinding uncomfortably against the rest of the picture’s leisurely stroll. Apatow wants to get these characters to a lightning-strike place of realization, but the page is missing fitting motivations, closing “Funny People” on a frustratingly curt note.

It’s not a head-snapping change of pace for Judd Apatow, yet “Funny People” is far more acidic and remorseless than anything he’s attempted before. It’s a terrific motion picture, with keen insight into the mind of the stand-up comic at his most game, blistered, and vulnerable, while remaining true to the spirit of solitude the occupation all but demands.